Method of cleaning oil wells



E. TILTON METHOD OF CLEANING OIL WELLS Nov. 30,1926.

INVENTDR Elvin Til'l'a'rz b WW7? ww hi attorney Original Filed August 12, 1922 Patented Nov. 30, 1926;

STATES PATENT OFFHCEQ" ELVIN TILTON, F WHEELING, WEST VIRGINIA, A SSIGN'OR 0F ONE-HALF TO G. MONROE WATSON, 0F WHEELING, WEST VIRGINIAL- METHOD OF CIlLEANING OIL WELLS.

Application filed Aug ust12, 1922, Serial No. 581,369. Renewed December 7, 1925.

'10 and entrance of water into the well, cause or contribute to this falling off in production. The most common cause of such falling off, however, is paratfine, a thick and gummy component of the oil which collects in the pores of the oil bearing sand adjacent the well and retards the flow of oil tl1ereinto.-

A general object of the invention is to provide a method of melting such parafiine and removing it from the well. v

Various processes have been practiced for the purpose of removing the deposits of parafiine. In some of such processes steam has been forced down the tubing or casing of the well and brought into contact with .25 the parafline coated portion of the well,

either with or without special apparatus for applying it thereto.

The disadvantages of this method are that a large proportion of the steain'tends to condense during its passage to the bottom of the well, so that when the point of its application has been reached the steam is inefiective in melting the parafiine. If the steam is introduced under high pressure, it tends 'to drive the melted parafline further into the pores of the sand so that production is more effectually cut ofi thanwas the case before the introduction of the steam.

Other processes which utilize the heat of 40 chemical actions or reactions to melt the parafline have also not been wholly satisfactory, because of the manner in which the chemicals have been introduced or applied. Previously the chemicals have been poured into the well in solution, or in a liquid state, or have been introduced at the mouth of the well in a solid state. In either case the heating effect is dissipated throughout the length of the casing or tubing and a corro- 59. sive effect is also exertedthereom The corrosive efi'ect is the more marked if the chemicals be dumped into the well while in a solid state, as in such case they-adhere to the casing or tubing, which is always in a moist condition,

A more specific object of the invention is, therefore, to provide a method for so intro ducing chemicals into the lower, or producing, zone of an oil well that their full action and heating effect is exercised in such zone and none dissipated in heating the casing or tubing of the well, so that the parafiine in the producing zone is completely liquified, and for raising the parafiine above the level of the oil sand, or producing zone of the well. In the accompanying drawings Figure 1 1s a vertical section through an oil well, showing a container for introducing one or mgre of the active chemicals. in operative position in the well ;Figure 2 is an elevation of the cage for supporting the inner container or receptacle which receives and discharges the chemical or chemicals; Figure 3 1s a fragmentary sectional view through the lower portion of the inner container, showing the same in closed position; Figure 4 is a fragmentary sectional view through the lower "portion of such container, showing the same in open or discharging position; Figure 5 is an elevation of a container of different form for containing other-chemicalor chemicals; and Figure 6 is a detail elevation of the valve of the acid container, illustrating a slight modification therein.

The apparatus shown for conducting the process comprises an acid container 1, shown .in Figures 1, 3 and 4 of the drawings, and an open receptacle or cage 2 for supporting the container 1. The acid container proper is an elongated receptacle, provided at its lower extremity with'a valved discharge orifice 4. The valve for closing the discharge orifice 4 comprises a stem 5, extending through the orifice, and a head 6 lying within the receptacle. The head 6 of the valve comprises a conical lower portion 7 arranged to fit the wall of the container adjacent the discharge orifice 1, and an upper portion 8,

which is shown as conical but which may be of any desirable rounded or tapered form.

' spending inner surface of the container adj'a.

ever, the head portions 7 and 8 may be separated by the ridge or head 10 shown in Figure 6 of the drawings, to additionally insure against displacement of the spheres from between the lower portion 7 of the valve head and the inner surface of the container.

The container proper, all parts of the valve, and the spheres for wedging the valve in open position, are all preferably made of lead in order that they may not be attacked by acid introduced in the container for the purpose of cleaning the well. p

In cleaning an oil well by the method of my present invention; the well is first pumped as dry as possible and the pump and tubing removed. A bailer is then used to remove any loose material which has not been reached by the pump.

Water is then poured into the well, the. volume of this water being preferably equal to the volume of acid which is to be intro- 39 duced. The total volume of both liquids trated sulphuric acid and is lowered into the well. When the container has been lowered to the bottom of the well, the valve stem 5 comes into contact therewith to open discharge orifice 4. The spheres 8 act as previously described to hold the lve in open position, and the container is then raised above the level of the liquid in the well and held in such position for a length of time sufficient for the discharge of the acid from the container.

When sufiicient time for the discharge of the acid has been allowed. the liquid'may beagitated'by raising'and lowering the container a short distance to thoroughly commingle the water and acid and to increase the effect upon the parafiine in the well. The acid is allowed to remain in this condition for a short time in order that the heat generated by the chemical combination of the acid and the water may have full opportunity to form a hot solution and highly heat the p'arafline in the well, melting some proportion thereof.

If desired, potassium dichromate'may be added to the acid. The function of the dichromate is to dissolve the final film of greasy material adhering to mineral matter in the well. It is therefore ofimportancc when the deposits, or the oil bearing sand itself, consist largely of a mineral substance,

such as limestone or calcium carbonate, which is attacked by sulphuric acid. In

such case the potassium dichromate by removing such film prevents the acid full opportunity to dissolve the deposits or to clean and enlarge the interstices or pores of the oil sand.

When the effect of the acid alone has been largely spent, the next step in the process usually is resorted to in order to insure a complete melting of the parafline. In conducting this step the cage 2, containing the receptacle 1, is first removed from the well. A second receptacle 11, is then filled with a suitable chemical for reacting with the sulphuric acid, preferably with sodium hydroxide (caustic soda). The receptacle or exciter 11 is formed of close wire mesh, and has a bail 12 forlowering it into thewell. This exciter 11 is filled with flake sodium hydroxide, and when lowered into the producing zone may be agitated by raising and lowering it a short distance in order to expedite the reaction between the sodium hydroxide and the sulphuric acid. This,

however, is generally unnecessary because the sodium hydroxide enters into solution and reacts with the sulphuric acid with great rapidity; creating an intense heat and thoroughly melting any parafline remaining in a solid state after the previous steps of the process. The exciter 11 may be raised, refilled, and again lowered to the operative zone as often as may be necessary to secure conplete neutralization of the. sulphuric aci The mixture is then allowed to remain in thr well a suflicient length of time to permit the melted parafiine to rise to the surface of the liquid.

The paraifine is then bailed out while still in a melted condition; and may be saved. if desired, either in a still liquid form or solidified by emptying it into cold water.

The solution remaining in the well is then also bailed'out, and the well is cleaned by flushing it with water which may be bailed or pumped out. As the acid has been completely neutralized, the well may be emptied without injury to the pump or other equip- -ment .used.

"It will be noted that the method described above results in completely and etliciently melting the parafline, without any inefiiciency resulting from the dissipation of heat Wasted in heating the casing or corrosion of the casing due to the adhesion of a chem- I ical thereto. It will be noted further that it is unnecessary in conducting/this method to use crude oil to act as a solvent of the.

the parafline itself, as it is melted and floats,

- to localize the heat of the chemical action.

In general the heatproduced by the entry of the acid into solution serves to melt a suilicient quantity of the paraiiin'e to form a slight initial seal, thus insuring the useful application of substantially all the heat generated by the subsequent reaction. The heating efi'ect is also cumulative, the action of the first chemical serving to preheat the liquid so that the heat produced by the reaction following-the introduction of the second chemical is higher than if introduced into a cold liquid or solution. In order to secure this effect the second chemical must obviously be introduced before the heat generated by the first action has been dissipated.

If the well is known to contain a relative ly slight deposit of parafline, the acid treatment alone will frequently prove sufficient to completely melt the same. In general, however, it is desirable to follow up this first step with the more intense heating secured by applying the sodium hydroxide to the zone from which the paraifine is to be removed.

When a maximum heating effect is attained. the oil bearing sand is cleaned and heated for an appreciable distance outward from the well itself. The heating in this outer zone serves to stimulate the flow of oil from the surrounding sand into the well. Such extended heating obviously occurs chiefly after the introduction of the sodium hydroxide and after the formation of an etlicient seal by the flotation of melted parafline. I

While the method has been described above as particularly intended for theremoval ofparafiine from oil wells, it will be understood that it also removes other deposits which tend to 'cut down production and which may be liquefied by heat or the interaction of the chemicals, as for example the deposit commonly known as B. S. tar, asphalt or the like.

n It is to be understood that an important feature of the invention resides in the method of application of the chemicals, wholly apart from the specific chemicals employed or their general classification. In this connection it is suflicient if the chemicals be such that. their action or reaction should. under the conditions, produce sufficient heat to melt the deposits.

It is also to be understood that the method of the invention is applicable to the cleaning of tanks, tubes. and similar containers. and that the appended claims are to be considered as referring to such application of the method as Well as to the more specific purpose of the invention.

What I claim:

1. The method of freeing an oil well of parafiine and other deposits, which consists in removing naturally occurring liquids from-the well, introducing water thereinto, discharging directly into the producing zone of the well an acid capable of forming a true solution with the water with a genera 7 tion of heat suflicient to melt a portion of the parafline and a water soluble dichromate to dissolve a portion thereof, and removing the melted and dissolved paratline from the well.

2. The method of freeing an oil well of 7 parafline and other deposits which consists in removing naturally occurring liquids from the Well, introducing water thereinto, discharging directly into the producing zone of the well an acid capable of forming a true solution with the water with a generation of heat sufiicient to melt a portion of the parafiine, introducing directly into the producing zone of the well a strong water soluble base in solid form to cause a further generation of heat by reaction with the acid solution, and removing the melted parafline from the well. i

3. The method of freeing an oil-well of parafline and other deposits which consists in removing naturally occurring liquids from the well, introducing water thereinto, discharging directly into the producing zone of the well an acid capable of forming a true solution with the water with a generation of 9 heat suflicient to melt a portion of the par.- afline and a water soluble dichromate to dissolve a portion thereof, introducing directly into the producing zone of the well a strong water soluble base in solid form to it cause a further generation of heat by reaction with the acid solution, and removing the melted parafiine from the well.

4. The method 'of freeing an oil well of parafiine and other deposits which consists in removing naturally occurring liquids from the well, introducing water thereinto, discharging directly into the producing zone of the well an acid capable of forming a'true solution with the water with a generation of heat suflicient to melt a portion of the paraffine. before total dissipation of heat thus generated introducing directly into the producing zone of the well a strong water soluble base in solid form to cause a further 1 generation of heat by reaction with the acid solution, and removing this melted paraffine from'the well.

5. The method of freeing an oil well of pa'raffine and other deposits which consists in removing naturally occurring liquids from the well, introducing waterthereinto, discharging directly into the producing zone of the well acid capable of forming a true solution with the water with a generation of 1 heat suflicient to melt a portion of the paraffine and a water soluble dichromate to dissolve a portion thereof, before total dissipation of the heat generated by the dissolution of the acid introducing directly into the 1 producing zone of the well a strong water soluble base in solid form to cause a further generation of heat by reaction with the acid solution, and removing this melted parafiine from the well.

6. The method of freeing an oil well of parafiine and other deposits which consists in removing naturally occurring liquids from the well, introducing water thereinto, discharging directly into the producing zone of the well an acid capable of forming a true solution with the water with a generation of heat suflicient to melt a portion of the parafline, permitting the formation of a seal over the solution by flotation of the melted- 15 paraifine, before total dissipation of the heat generated by the dissolution of the acid introducing directly into the producing zone of the well a strong water soluble base in solid form to cause a further generation of '20 heat by reaction with the acid solution, and

removing the melted parafiine from the well. In testimony whereof, I hereunto set my hand.

ELVIN TILTON. 

